Recently, as next-generation nonvolatile semiconductor memories, resistance change memories have been attracting attention, such as a resistive RAM (ReRAM) in which a variable resistive element serves as a memory element, and a phase change RAM (PCRAM) in which a phase change element serves as a memory element.
These resistance change memories are characterized in that a memory cell array is a cross-point type and a higher memory capacity is thus enabled by three-dimensional integration, and also characterized by being capable of the same high-speed operation as that of a DRAM.
In the resistance change memory, the cross-point type memory cell array includes a plurality of cell units. The cell unit includes a memory element and a non-ohmic element (e.g., see Jpn. Pat. Appln. KOKAI Publication No. 2009-123725).
Such a resistance change memory, when put into practical use, can replace, for example, a NAND flash memory as a file memory and a DRAM as a work memory.
However, in order to put the resistance change memory into practical use, characteristics of the non-ohmic element have to be improved.